Phytogenic feed additives may boost broiler growth, performance

In a wheat diet, additive thymol and carvacrol (T+C) and an NSP-degrading enzyme may improve broiler growth and health.

A team of international researchers presented their work with the additives in the journal of Animal Feed Science and Technology​.

They sought to evaluate the use of the phytogenic treatments with or without an NSP-degrading enzyme (E) and the effect on broiler nutrient retention, cecum microbes, volatile fatty acid (VFA) profiles and intestinal health, they said.

“Thymol + carvacrol, in combination or not with an NSP-degrading enzyme, improved growth performance, enhanced nutrients retention, increased total VFA, reduced cholesterol and modulated intestinal microbial counts in broilers fed on a wheat-based diet,”​ they said.

Why phytogenic treatments​

Researchers examined the use of an enzyme with thymol + carvacrol as a potential replacement for antibiotic growth promoters in poultry feed, they said.

Wheat diets contain more anti-nutritional factors including insoluble non-starch polysaccharides (NSP) than a corn diet, said the scientists. Those factors have been linked to some negative side effects.

“Compelling evidence indicates that broilers fed diets based on wheat, barley, or rye suffer from reduced crude protein (CP) and fat digestibility, and a reduced apparent metabolizable energy content (Mathlouthi et al., 2002), which resulted in depressed body weight gain and increased feed conversion ratio (Lázaro et al., 2003),” ​they said.

Positive outcomes from using an enzyme supplement with such diets have already been established, said the researchers. But less is known about the use of an enzyme with a phytogenic feed additive.

“Phytogenic feed additives (PFA) may positively affect poultry health and productivity,”​ they said. Thymol and carvacrol have been linked to antimicrobial and antifungal activities.

It was anticipated that the feed additives might positively influence broiler growth and performance, they said.

Experiment​

In the experiment, researchers fed 360 broiler chicks one of six experimental diets for a period of 42 days, said researchers. “Each treatment was replicated five times with 12 chicks per replicate,”​ they added.

The diets included a control with no T+C and two levels of T+C, 100 and 200 mg/kg of diet and two amounts of enzyme 0 or 0.5g/kg of the diet, they said. The T+C supplement used was Next enhance150 and the enzyme was Endofeed W.

Feed consumption and body weight were measured by pen on days 10, 24 and 42, they said. Average daily feed intake (ADFI), feed efficiency (G:F) and average daily gain (ADG) were determined for the periods.

A selection of birds was harvested on day 24 to collect digesta from duodenum, jejunum and ileum, they said. Cecal contents were collected on days 24 and 42 and blood samples were taken on day 40.

Results​

There was no interaction found between the enzyme and T+C for the considered areas, said researchers. No significant effects were seen for average daily feed intake.

When compared with control birds, those getting diets that included T+C  or the enzyme had a higher final body weight, better feed efficiency and boosted average daily gain, they said.

“For the whole period, E and the two levels of T+C supplementation improved (P < 0.05) final body weight by 5.1 and 5.2 and 6.1%, respectively, ADG by 5.5 and 5.3 and 6.2%, respectively, and G:F by 5.8 and 5.7 and 7.1%, respectively, of birds fed wheat-based diets,”​ they said.

The viscosity of the digesta in the small intestine was reduced in the diets the enzyme, they said.  It was similarly reduced in the jejunum and ileum for treatments with T+C.

Both sets of birds had an improved retention of dry matter, protein and energy, said the scientists.

“Dietary supplementation with E and T+C increased (P < 0.01) total VFA and acetate levels at d 24 and 42, whereas the level of butyrate decreased (P < 0.01),”​ they said. “Escherichia coli and Clostridium perfringens counts were lower (P < 0.01) than controls, and Lactobacilli counts were higher (P < 0.01), in birds fed on diets supplemented with enzyme or T+C at the rate of 200 mg/kg.”​

The enzyme supplement raised serum triglycerides, total cholesterol, protein amounts, and concentrations of albumin and globulin, they said. And it decreased the length of the duodenum, jejunum and ileum, they said.

However, use of the T+C additive reduced total cholesterol, total protein and albumin, they added.